Nirguna Brahman - creator god without attributes (a contradictory statement in itself, for it is absurd to say there is a thing but has no qualities).
Nirvana - the end of suffering, elimination of greed, hatred and ignorance. It is neither a being nor a place but an experience.

1Myriad dharmas are only mind.
Mind is unobtainable.
What is there to seek?2If the Buddha-Nature is seen,
there will be no seeing of a nature in any thing.3Neither cultivation nor seated meditation —
this is the pure Chan of Tathagata.4With sudden enlightenment to Tathagata Chan,
the six paramitas and myriad means
are complete within that essence.

According to whom? ie. many different schools and systems use these terms, and their definitions are not the same. It may help to be more specific before asking questions like "What's the difference?"

But one point that can be made, is this: The term "nirvana" is much older, and the term "nirguna brahman" is from a period of Vedanta which has been heavily influenced by Buddhist (& Jain, etc.) thought. Be careful of anachronisms in any comparisons.

Nirguna Brahman, according to Advaita (as far as i am aware) is the non dual state of samata or samatman. there is still a form of self in this realization (though it is not individual), which needs the rope of wisdom to kill itself. (see snake and rope). it is a nondual state in which all things are seen as the same conciousness, but in this state consciousness has not yet been swept away. there is no relationship between nirguna brahman/brahman atman and nirvana. nirguna brahman can become sunyatman, empty of self. when it does so, it ceases to be brahman, or anything. sunyatman is the realization experientially of what always was... no self whatsoever.

i am only speaking from personal experience, this may be considered unhelpful, and if it is, i apologise for any apparent misdirection on my part.

best wishes, White Lotus. x

in any matters of importance. dont rely on me. i may not know what i am talking about. take what i say as mere speculation. i am not ordained. nor do i have a formal training. i do believe though that if i am wrong on any point. there are those on this site who i hope will quickly point out my mistakes.

"Just say the nembutsu and be liberated" Shinran Shonin
"However hard it may be to bid farewell to this world, when the conditions that bind us to this saha [samsara] realm run out, we are powerless to do anything as the final hour arrives and we are swept away to that Land." -A Record in Lament of Divergences

consciousness is one of the five skhandas, it needs to be swept away if a state of sunyatman is to be attained. every 'thing' must be swept away in order to attain sunyatman, the emptiness body. once everything has been swept away including perception of a self, then one perceives the base on which emptiness/form rests. there is no direction for the mind then, but to become the base. 'this' is acheived by 'this'. this cannot be annihilated, it is absolutely eternal, indestructible, immutable, unchanging. it is what we call suchness.

its reassuring that in ones practice one is still 'this', inspite of having brushed away the five skhandas and direct experience of self/the 5 skhandas.

having said that there is still 'this', if a less developed mind annihilates the five skhandas one can be trapped in limbo. so it can be dangerous to do so. by limbo i mean that the 'this' that the mind perceives is corroded and replaced by nothingness.

please note that this is only my own experience, and is by no means orthodox. this is the direction that my path has taken.

now, i would say that no special experience or realization is needed. that all of the states mentioned above are unnecessary. that, the buddha is the buddha regardless of any forms of attainment or lack of attainment.

realization of no-self is not necessary.
the bhumis are not necessary.
knowledge of the true nature is not necessary.
meditation is not necessary.
enlightenment is not necessary.

you have it, just as you are.

it is not necessary to follow the spiritual path to realize this. there is nothing to realize. everyone and everything is perfect, just as it is. i follow a path, because i do not wish to be negatively affected by cause and effect, but fundamentally even cause and effect are only apparent. actually there is no cause nor effect. at root all is empty. there is nothing to worry about.

suchness:-this is it,
Tom is it,
the computer is it,
my meditation is it,
my lack of meditation is it,
the sky is it,
pain is it,
comfort is it,
pop music is it,
jazz is it,
romantic novels is it,
rock is it,
classics are it,
just chilling is it,
working your ass off is it,
so... just make a cup of tea!

you cant get away from it... all is perfect enlightenment. just as it is.
nothing to be, nothing to become. just as you are. this is it.

love, White Lotus. x

WHO NEEDS TO SWEEP AWAY CONSCIOUSNESS?!!!
NO ONE.

in any matters of importance. dont rely on me. i may not know what i am talking about. take what i say as mere speculation. i am not ordained. nor do i have a formal training. i do believe though that if i am wrong on any point. there are those on this site who i hope will quickly point out my mistakes.